(calendar-date-echo-text): Doc fix. Add default :value for sexp type.
(calendar-month-edges): New variable.
(calendar-month-edges): New function.
(calendar-recompute-layout-variables): Set calendar-month-edges.
(calendar-intermonth-header, calendar-intermonth-text): New options.
(calendar-insert-at-column): New function.
(calendar-generate-month): Use calendar-insert-at-column.
Handle intermonth text. Add 'date property.
(calendar-column-to-month): Remove function.
(calendar-column-to-segment): New function.
(calendar-cursor-to-date): Use calendar-column-to-segment. Check 'date property.
(calendar-print-other-dates): Handle mouse events.